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V.  s    DEPAR  \WY.\  X   I  »l      \<  iRICI   I    I  I   l<  I 
0MOLOG1  No.  158. 

I      O.  H<  W  ARD,   Kninmologitt  and  Chirf  ol  Bufe.ii. 


TIIK  CLOVER   MITE 


1".  M.  WEBSTER, 
In  <  Tuargt  of  Ctr 


r    IRS— 12 


.OVESKMENT    • 


BUREAU    OF    ENTOMOLOGY. 

L.  O.  Howard,  Entomologist  and  chief  of  Bureau. 

C.  L.  Marlatt,  Entomologist  and  Acting  Chief  in  Absence  of  Chief. 

R.  S.  Clifton,  Executive  Assistant. 

W.  F.  Tastet,  Chief  Clerk. 

F.  H.  Chittenden,  in  charge  of  truck  crop  and  stared  product  insi  ct  investigations. 

A.  D.  Hopkins,  in  charge  of  forest  insect  investigations. 

W.  I>.  Hunteb,  in  charge  of  southern  field  crop  insect  investigations. 

F.  M.  Websteb,  in  charge  of  cereal  and  foragt   insect  investigations. 

A.  L.  Qtjaintance,  i/n  charge  of  deciduous  fruit  insect  investigations. 

E.  F.  Phillips,  in  charge  of  bee  culture. 

D.  M.  Rogers,  i/n  charge  of  preventing  spread  of  moths,  field  work. 

Roll.v  P.  Currie,  in  charge  of  editorial  work. 

Mabel  Colcord,  in  charge  of  library. 

Cereal  and  Fobage  Insect  Investigations. 

F.  M.  Webster,  /"//  charge. 

Geo.  I.  Reeves,  VT.  J.  Phillips.  C.  N.  Ainslie.  E.  O.  (J.  Kelly.  T.  D  Crbahns, 
Harry  S.  Smith,  Geo.  <;.  Ainslie.  .1.  A.  Hyslop,  W.  II.  Walton.  J.  T.  Monell, 
J.  J.  Davis,  T.  H.  Parks,  R.  A.  Vickery.  V.  L.  Wii.permvtii.  E.  <;.  Smyth, 
Herbert  T.  Osborn,  Philip  Luginbill,  C.  W.  C-BfcEL,  E.  J.  Vosler.  R.  N.  Wil- 
son,  Vebnon  King,  George  R.  Smith,  Irving  Crawford,  entomological  as- 
sistants. 

Nettie  S.  Klopeer.  Ellen  Dashiell,  preparators. 

Miriam  Welles  Reeves,  collaborator. 
u 


Circular  No.  158. 


. 


United  States  Department  of  Agriculture, 

BUREAU    OK    ENTOMOLOGY. 
L.   O.    HOWARD,    Entomologist    .ml    Chid  «.f    Hurenu. 


THE  CLOTEB   Mill.. 

yobia  prat i  n*h   < iarman.  > 
By  r.  M    w  i  B8i 
In  Cha  real  'iinl  Foraffi    Insect  Investigations. 

[NTHOD1  I   HON. 

The  minute  organism  known  ;i-  the  clover  mite  (fig.  Ii   is  :  • 
true  insect,  but  belongs,  with  the  spiders,  to  a  rery  extensive  group 
the  adults  of  which  possess 
eight  legs,  whereas  true  in- 
sects have  only  six  legs. 

There  are  a  greal  many 
species  of  these  mite-  and 
they  differ  widely  among 
themselves  in  habits.  Sonic 
make  galls  on  the  leaves  of 
trees  and  shrubs :  some,  like 
the  one  which  commonly  at- 
tacks the  currant,  arc  known 
as  blister  mites,  as  they 
cause  blisters  on  leave-: 
others  are  para-it  ic  on  man. 
as  the  itch  mite;  while  -till 
others,  like  the  Trombidium, 
arc  parasitic  on  insects. 
Another.  P<  dit  uloid<  s  >••  n- 
Nev  p.,  is  parasitic 
on  insects  hut  also  attack- 
man.  The  one  here  treated 
lives  on  the  surface  of 
leave.-  of  trees  and  plant-. 
but  does  not  cause  galls  or 
blisters.  It  is  a  near  relative 
of  the  notorious  red  spider. 

The  clover  mite,  also  known   a-  the  brown   mile,   i-  of  a   twofold 
interest     It  attack.-  the  leave.-  of  clover,  grasses,  and  fruit  and  other 

1 


i. — The    clover    ml 

Enlarcod  :  minimi   size  shown  by  line  at   ri^-ht. 


Z  THE    CLOVER    MITE. 

trees,  feeding  upon  and  often  destroying  (hem;  beside-,  during-  winter 
and  spring  it  frequently  swarms  in  dwellings,  often  crawling  about 
in  myriads  over  windows,  furniture,  picture-,  curtains,  etc. 

The  species  was  first  described  in  1885.1  but  it  was  observed  in  great 
abundance  about  Washington,  D.  C.  by  Mr.  Theodore  Pergande,  of 
the  Bureau  of  Entomology,  as  early  as  1878.  While  described  as  a 
clover-infesting  species,  having  been  found  infesting  clover  leaves  by 
both  Mr.  Pergande  and  Prof.  IT.  Garman,  yet  taken  as  a  whole 
throughout  its  known  area  of  distribution  it  is  probably  of  more  im- 
portance to  the  fruit  grower  than  it  is  to  the  farmer.  While  east  of 
the  semiarid  region  it  is  found  largely  on  clover  and  bluegrass,  it 
is  at  present  largely  an  orchard  pest  west  of  about  longitude  100°. 


Fig.   2. — Map   showing  the   distribution   of  the  clover   mite    {Bryobia   pratensis)    in    the 
United  States  in  1911.      (Original! 

DISTRIBUTION. 

With  the  possible  exception  of  Georgia  the  pest  seems  to  occur 
generally  over  the  whole  country,  except  perhaps  in  the  Gulf  States 
and  the  Dakotas,  though  just  why  it  should  not  be  found  even  there 
can  not  now  be  explained.  (See  map,  fig.  2.)  Mr.  Marlatt2  states 
that  it  has  been  reported  from  Tennessee,  and  in  the  Sierra  Nevada 
Mountains  in  California  and  Rocky  Mountains  in  Montana  at  ele- 
vations of  from  7.000  to  8.000  feet,  but  exact  localities  are  not  given. 

The  mite  was  described  from  the  leaves  of  red  clover  (Trifolium 
pratense)   from  which  it  derives  its  last  or  specific  name.     Accom- 


1  Fourteenth  Rept    St.  Ent.  111.,  pp.  73-74,  1885. 
2Cir.  19,  Div.  Ent.,  U.  S.  Dept.  Agr.,  1897. 


rHE  CLOVER   MITE.  .'{ 

panying  the  original  description  is  the  following  note  b\  Dr.  S.  \. 
Forbes,  State  entomologisl  of  Qlinois: 

ai   Normal,  ea  May,  the  general  occurrence  'i  conapli 

brownish  red  ■■  ■  i i •-  was  noticed  upon  clover  and  bluegrass    the  former  "i"  these 
plants,  especially,  sometlmef   Buffering  Beverelj    from  the  peal      The  lea  i 
the  clover  turned  yellow   and  their  growth  w  ed  where  the  mite  wai 

■bandant     I'be  effecl  upon  the  blues.  similar. 

\-  a  matter  of  fact,  the  bureau  records  contain  reports  of  the 
occurrence  "I"  the  species  over  the  territory  indicated  by  the  map 
(fig.  •_').  These  records  illustrate  its  great  varietj  of  food  plant-  a- 
well  as  th«'  effect  of  climatic  and  other  natural  conditions  upon  its 
habits;  they  are,  however,  far  too  voluminous  to  include  in  a  publi- 
cation of  the  nature  of  this  circular. 

Dl  B<  RIPTION8. 

These  mites  are  sufficiently  shown  in  figure  1  to  obviate  the  n< 
-itv  for  a  lengthy  description.  When  young  thej  are  of  a  decidedly 
red  color,  but  become  brown  when  fulh  developed,  even  then  being 
smaller  than  the  head  of  a  pin.  They  are  very  familiar  objects 
moving  about  over  clover  leaves  that  have  a  more  or  less  whitish 
appearance.    The  discoloration  of  the  leaves  is  in  part  due  to  the 

feeding  of  the  mitt'-,  and  also  to  tin'  tiny  white  web  that  they  leave 
behind  them  a-  the\  move  about.  The  eggs  are  minute,  round,  red, 
and  shining. 

FOOD  PLAN  IS. 

From  the  foregoing  it  will  be  observed  that  this  mite  i-  ;i  | 
feeder  and  may  be  expected  to  attack  clover-,  alfalfa,  bluegrass,  and 
probably  other  grasses,  among  them  timothy.    It  may  affect  oats  and 

probably  other  grains  including  buckwheat.    Mr.  <i *ge  P.  Weldon 

■  all-  attention  to  the  fact  that  it  had  not  been  observed  attacking 
apricot  or  quince  and  appeared  less  on  peach  than  on  most  other 
fruit-  in  Colorado.1 

Judging  from  what  we  know  of  an  allied  species,  Tetranychtu 
h'nhiu  tdatus  Harvey,  the  jh*- t  i-  likely  to  become  more  abundant 
and  injurious  in  the  drier  sections  of  the  country  than  where  the 
atmosphere  i-  more  humid.  It  does  not  necessarily  follow  that  the 
mite  will  attack  the  fob  a  ire  of  the  tree  on  which  it  has  deposited  eggs. 

-i  \-c\  \t.  HIST  'i;i  . 

Throughout  the  eastern  portion  of  the  country  the  life  cycle  and 
seasonal  history  of  this  species  probably  do  not  materially  differ 
from  those  of  other  mite.-.    With  the  coming  >•(  cold  weather  in  late 

'  i  •■     dt 

«Bul.   162  jr.  Coll.   Exp.  Sta..  p.  6.  1909. 


4  THE    CLOVBB    BUTE. 

autumn  or  early  winter  the  mites  apparently  cease  to  deposit  egg-. 
and  thus  operations  are  simply  suspended  until  the  coming  of  warm 
weather  in  spring,  when  the  eggs  promptly  hatch  young  mites.  This 
is  clearly  shown  by  the  observations  of  Mr.  Pergande. 

A-  will  be  observed,  the  presence  of  mies  in  dwellings  during 
fall  and  spring  is  of  common  occurrence.  Do  they  deposit  eggs  and 
do  these  eggs  hatch  there  {  It  may  be  stated  thai  both  eggs  and  mite 
were  received  from  "Williainsport.  Pa..  December  11.  180G,  and  that 
the  eggs  hatched  en  route.  Also,  as  observed  by  the  writer,  the  mite- 
entering  a  dwelling  in  Lafayette.  Ind..  during  December.  1880,  when 
the  weather  was  very  mild,  were  at  first  full  grown,  but  young 
appeared  later  in  the  month.  Whether  nates  seek  out  dwellings  in 
which  to  continue  reproduction  but  die  out  for  lack  of  food,  or 
whether  they  enter  them  for  the  purpose  of  hibernation,  is  not  clear. 
It  is  very  clear,  however,  that  they  do  not  go  into  hibernation  in 
May.  a  time  when  their  occurrence  in  dwelling-  is  of  equally  common 
occurrence.  Furthermore,  our  notes  show  that  complaints  of  these 
mites  entering  dwellings  almost  invariably  come  from  the  eastern  and 
cooler  sections  of  the  country,  the  reports  from  McCook,  Xebr.,  and 
Denver,  Colo.,  being  the  only  exceptions  in  the  West.  Mr.  George  P. 
Weldon.  who  studied  the  species  in  Colorado.1  states  that  it  winters 
there  principally  in  the  egg  stage  and  that  practically  no  living 
mites  can  be  found  abroad  after  August  1.  Hatching  begins  about 
May  1.  and  there  are  probably  three  generations  annually  in  that 
region. 

REMEDIAL   AXD    PREVENTIVE    MEASURES. 

Tobacco  preparations  applied  in  the  form  of  a  liquid  spray  are 
quite  effective  in  destroying  the  mite,  but  do  not  destroy  the  egg, 
and  therefore  offer  only  temporary  relief.  Mr.  Weldon  found 
that  flowers  of  sulphur  dusted  on  foliage  during  early  morning 
was  more  effective  in  destroying  the  mites.  A  liquid  spray  of  1 
pound  flowers  of  sulphur  mixed  in  -1  gallons  of  weak  soapsuds,  1 
pound  of  soap  to  100  gallons  of  water,  was  very  effective  and  ap- 
peared to  be  lasting  in  its  effects.  This  last  can  be  easily  applied 
to  lawn--  and  grounds  where  the  mites  are  at  work  and  also  in 
field-  of  clover  or  alfalfa  in  case  the  depredations  are  confined  to 
-mall  spots  or  areas.  The  eggs  can  be  destroyed  on  the  trunks  of 
trees  by  the  use  of  strong  kerosene  emulsion.  The  writer  has  re- 
ceived reports  of  good  results  in  driving  the  mites  away  from  dwell- 
ings by  placing  oil  of  pennyroyal  in  small  shallow  dishes  in  the 
looms  where  the  mites  occur.  This  measure  does  away  with  the 
disagreeable  feature  of  fumigation  with  fumes  of  sulphur  or  dust- 
ing with  insect  powder,  and  the  odor  of  the  oil  is  not  disagreeable 
to  people  using  the  rooms. 

1  Loc.   cit.,   p.    3,   October.    1909. 


Till     ii  i>\  I  i;    Ml  I  1  .  O 

s  \  i  i  1:  m     i  \  l  \i  II  S. 

The  insect  enemies  "l"  ilii-  mite,    o  far  as  recorded,  are  eerj   few. 

(  tetober  28,  L889,  Mi.  Perg  md<  reared  one  of  the  common  clothes 
moths  (Tineola  hiseUiella  Hiibn.)  from  small  caterpillars  that  be 
had  observed  to  feed  upon  tl 

Mr.  Weldon '  gives  as  enemies  "f  the  red  pider  (Tetranychtu 
h'nini<  uliit'ts  Harv.)  a  minute  black  lady-beetle,  Scymnu*  punctum 
Lee.   MiLr-  3)  and  lace-winged  flies.      \-  there  are  many  speci< 


*  O 


IT..     '■     S  "riiMu.«  punctum,  a  laih  beetle  enemy  of  the  clover  mlt'  Bgg;   ''•  larva; 

e,  papa;  •'.  adult.     All  n  .  '.  ■ .  Red    iwn  fr..m  Weldon:  <'.  original. 

the  Scymnus  and  of  lace-winged  flies,  ii  is  nol  at  all  unlikely  that 
some  of  them  prey  upon  the  clover  mite. 

A.pproi ill : 
James  Wn 

i  y  of  . \>i> icvltun  . 

Washington,  D.  (  ..  April  18,  1912. 


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